def avg_capital(a, r, n):
    monthly_principal = a / n  # 每月应还本金
    total_payment = 0  # 总还款额
    remaining_principal = a  # 剩余本金
    for i in range(1, n + 1):
        interest = remaining_principal * r  # 每月应还利息
        total_payment += monthly_principal + interest  # 本金加利息
        remaining_principal -= monthly_principal  # 剩余本金减去已还本金
    return round(total_payment, 2)

def avg_capital_interest(a, r, n):
    monthly_payment = (a * (1 + r)**n * r) / ((1 + r)**n - 1)  # 每月固定还款额
    total_payment = monthly_payment * n  # 总还款额
    return round(total_payment, 2)  # 返回总还款额，保留两位小数

def campus_loan(a, r, n):
    total_payment = 0  # 总还款额
    monthly_interest = a * r  # 每月应还利息
    for i in range(n):
        total_payment += monthly_interest  # 每月利息累加到总还款额
    total_payment += a  # 加上原始贷款本金
    return round(total_payment, 2)  # 返回总还款额，保留两位小数

if __name__ == '__main__':
    a = eval(input())
    r = eval(input())
    n = eval(input())
    # print(f"{avg_capital(a, r, n)} {avg_capital_interest(a, r, n)}")
    print(campus_loan(a,r,n))